CN111225853B

CN111225853B - Wing pitch actuation system for an electric vertical take-off and landing (VTOL) aircraft

Info

Publication number: CN111225853B
Application number: CN201880061285.6A
Authority: CN
Inventors: A·D·摩尔
Original assignee: Emso Innovation Pte Ltd
Current assignee: Emso Innovation Pte Ltd
Priority date: 2017-09-22
Filing date: 2018-09-06
Publication date: 2024-04-05
Anticipated expiration: 2038-09-06
Also published as: RU2020110837A; EP3684687B1; EP4219303A1; EP3684688A1; EP3684688A4; BR112020005611A2; US20200231277A1; JP7457175B2; RU2020110837A3; RU2020110832A3; PH12020500508A1; AU2018337069A1; JP2020534212A; IL273314B1; AU2018337666A1; KR102650998B1; US20200223542A1; WO2019056052A1; IL273314B2; CN111247066A

Abstract

A vertical take-off and landing (VTOL) aircraft (10) includes a fuselage (24), first and second front wings (20, 22), and first and second rear wings (30, 32), each having a fixed leading edge (25, 35) and a tail control surface (50) that pivots about a generally horizontal axis. An electrically powered rotor (60) is mounted to the wing (20, 22, 30, 32), the electrically powered rotor (60) pivoting with the tail control surface (50) between a first position in which each rotor (60) has a substantially vertical axis of rotation and a second position in which each rotor (60) has a substantially horizontal axis of rotation; wherein at least one of the wings (20, 22, 30, 32) has a first electrically powered rotor and a second electrically powered rotor (60), each mounted with non-parallel axes of rotation such that the thrust line of the first electrically powered rotor and the thrust line of the second electrically powered rotor are different.

Description

Wing pitch actuation system for an electric vertical take-off and landing (VTOL) aircraft

Technical Field

The present disclosure relates to a wing tilt actuation system for an electric vertical take-off and landing (VTOL) aircraft. In particular, the present invention relates to wing tilt actuation systems and mechanisms for electrically powered VTOL aircraft having passenger and/or military applications.

Background

The VTOL aircraft can take off and land vertically or at some angle near vertical. Aircraft of this type include helicopters and certain fixed wing aircraft, commonly used for military applications. Advantageously, the VTOL aircraft allows for landing in a limited space, which eliminates the need for large runways and allows for landing on smaller spaces as well as on tarmac such as ship decks and buildings and other structures.

A helicopter is an aircraft in which both lift and thrust are provided by the rotor. Some of the problems associated with helicopters may be problematic in certain applications, such as high levels of noise output. One such disadvantage associated with helicopters relates to rotor designs that are critical to flight. There is typically no redundancy in its design, which means that the operation of the (or each) rotor is critical. The lack of redundancy means that all the components of the rotor and the transmission must have a large safety factor, which increases the weight and the manufacturing costs of the helicopter considerably.

Electric aircraft are of increasing interest for various commercial and safety reasons. In recent years, there have been many developments in drone technology, which typically utilizes a plurality of electrically powered rotors spaced around the pitch diameter. Unmanned aerial vehicles are typically operated by electrically powered rotors, each of which rotates about a generally vertical axis.

While unmanned aerial vehicles are becoming increasingly commercially viable for transporting smaller payloads, they are typically limited to relatively low flight speeds due to the vertical axis of rotation of the rotor. Furthermore, they tend to have a rather low range of travel during each battery charge.

Tilting aircraft wing craft are available and generally operate according to the principle of a vertical propeller axis for lifting and lowering, and the wing is configured to tilt between a configuration in which the propeller has a vertical axis for lifting and a configuration in which the propeller has a horizontal axis for forward flight.

The above-mentioned tilting wing arrangement provides the advantage of landing in areas with limited free space available, such as aircraft carriers and tarmac. In addition, a tilting wing aircraft is capable of providing a flight speed comparable to a conventional propeller driven fixed wing aircraft.

Tilting wing aircraft typically have an electric motor or gas turbine engine for driving a propeller or ducted fan mounted directly to the wing. The entire wing rotates between vertical and horizontal to tilt the thrust vector from vertical to horizontal and back.

By definition, a "thrust line" (also referred to as a "thrust vector") is the thrust of a propeller and is approximately the same as the axis of rotation of the propeller. The "hinge line" is the hinge axis of rotation.

Existing tilting wing aircraft have some inherent disadvantages. One disadvantage is associated with the actuators and bearings or other such mechanisms required for controlling the pitch angle of the wing between the lift/lower configuration and the forward flight configuration. The actuators may also be used to lock the wing at a desired tilt angle during forward flight. In practice, however, the actuators and bearings can add significant weight to the aircraft. This results in a reduction in the amount of payload such as personnel or cargo that can be transported. Furthermore, due to the critical nature of the wing pitch actuation system and bearings, the assembly must be designed with sufficient redundancy to reduce the risk of catastrophic failure.

Currently, the Lilium avigation (Lily Aviation) is designing and testing an electric VTOL Jet (electric VTOL Jet), which is under the trademark Lilium Jet ^TM . The prototype is intended for use as a lightweight commuter aircraft for two passengers, having two wings and approximately 36 motors.

Lilium Jet ^TM Disadvantages of the type of aircraft are associated with the electric motor, which is a closed fan type motor. This arrangement is highly energy consuming, resulting in a given cell sizeReduced possible flight range.

In addition, enclosed fans can only be operated for lifting on hard surfaces such as designated tarmac and runways, etc. This limits the availability of the aircraft and prevents the aircraft from operating on non-hard surfaces (such as parks, fields and gardens) during take-off and landing. For military applications, this is undesirable and cannot meet the need for temporary landings in remote areas.

Another concept of VTOL aircraft is the S2 electric of Joby avitation ^TM . This design has a fixed wing with multiple (preferably four) motors mounted on each wing. Four additional motors are mounted at the rear stabilizer or tail. A disadvantage of this concept aircraft is that each motor is actuated independently, requiring a separate actuator for each motor. As mentioned above, this requires significant additional weight for actuating the motor system.

Disclosure of Invention

It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or to provide a useful alternative.

Summary of the invention

In a first aspect, the present invention provides a vertical take-off and landing (VTOL) aircraft comprising:

a body;

first and second front wings mounted to opposite sides of the fuselage;

first and second rear wings mounted to opposite sides of the fuselage;

each wing has a fixed leading edge and a trailing control surface that pivots about a generally horizontal axis;

a plurality of motors having rotors mounted to the wing, the rotors pivoting with the tail control surface between a first position in which each rotor has a substantially vertical axis of rotation and a second position in which each rotor has a substantially horizontal axis of rotation;

wherein at least one of the wings has a first motor with a first rotor and a second motor with a second rotor, each mounted with non-parallel axes of rotation such that the thrust line of the first rotor and the thrust line of the second rotor are different.

The thrust lines of the first rotor are preferably angled to pass over the hinge line and the thrust lines of the second rotor are angled to pass under the hinge line.

The axis of rotation of the first rotor is preferably angled upwardly relative to a plane passing through the nose and tail of the control surface, and the axis of rotation of the second rotor is angled downwardly relative to a plane passing through the nose and tail of the control surface.

When the first rotor and the second rotor are operated at the same rotational speed, the rotational moments generated by each of the first rotor and the second rotor and acting on the control surface preferably cancel each other out.

The first motor and the second motor are preferably pivotally mounted to the underside of the fixed leading edge.

The first motor and the second motor are preferably grounded to the tail control surface.

In a second aspect, the present invention provides a vertical take-off and landing (VTOL) aircraft comprising:

a body;

first and second front wings mounted to opposite sides of the fuselage;

first and second rear wings mounted to opposite sides of the fuselage;

a plurality of motors, each having a rotor mounted to the wing, the motors and rotors pivoting with the tail control surface between a first position in which each rotor has a substantially vertical axis of rotation and a second position in which each rotor has a substantially horizontal axis of rotation;

wherein at least one of the wings has a first motor with a first rotor and a second motor with a second rotor offset relative to the upper and lower surfaces of the wing.

Preferably, the first rotor is positioned below the lower surface of the wing and the second rotor is positioned above the upper surface of the wing.

The motors and rotors are preferably distributed along the wing at locations below the lower surface of the wing and alternately above the upper surface of the wing.

The distal portion of each front wing furthest from the fuselage is preferably connected to the distal portion of an adjacent rear wing by a connecting member, thereby defining a box-shaped wing structure.

Each front wing is preferably connected to an adjacent rear wing by one or more struts or ties.

The control surface preferably pivots through a range of about 80 degrees and 100 degrees. The control surface preferably pivots through a range of about 90 degrees.

In a third aspect, the present invention provides a vertical take-off and landing (VTOL) aircraft comprising:

a body;

first and second front wings mounted to opposite sides of the fuselage;

first and second rear wings mounted to opposite sides of the fuselage, each front wing being connected to an adjacent rear wing by a distal connecting member or strut to define a box-like wing or strut support wing (strut braced wing) structure;

a plurality of motors having rotors mounted to the wing, the motors having rotors pivoting with the tail control surface between a first position in which each rotor has a substantially vertical axis of rotation and a second position in which each rotor has a substantially horizontal axis of rotation.

At least one of the wings preferably has a first motor with a first rotor and a second motor with a second rotor offset relative to the upper and lower surfaces of the wing.

The first electrically powered rotor is preferably positioned below the lower surface of the wing and the second electrically powered rotor is preferably positioned above the upper surface of the wing.

In a fourth aspect, the present invention provides a vertical take-off and landing (VTOL) aircraft comprising:

a body;

first and second front wings mounted to opposite sides of the fuselage, each wing having a fixed leading edge and a tail control surface that pivots about a generally horizontal pivot axis;

each wing has a first motor with a first rotor and a second motor with a second rotor, the motors and rotors pivoting with the tail control surface between a first position in which each rotor has a substantially vertical axis of rotation and a second position in which each rotor has a substantially horizontal axis of rotation,

a control system for controlling each motor and rotor;

wherein the control system is configured to selectively operate the first motor and first rotor and the second motor and second rotor at different rotational speeds to generate a rotational moment to pivot the control surface about a pivot axis.

At least one of the wings preferably has a first electrically powered rotor and a second electrically powered rotor, wherein the thrust line of the first electrically powered rotor is angled to pass over the hinge line and the thrust line of the second electrically powered rotor is angled to pass under the hinge line.

The electrically powered rotor is preferably positioned on the underside of each wing.

Each rotor is preferably offset longitudinally with respect to the axis of rotation of said rotor with respect to an adjacent rotor mounted on the same wing.

Each rotor outer diameter preferably overlaps and is mounted on the same wing relative to an adjacent rotor outer diameter when viewed in a plane extending perpendicular to the axis of rotation of the rotor.

The fuselage preferably has a cabin which is accessed through a door which faces forward and is hinged at an upper region to open upward.

The first rear wing and the second rear wing preferably each comprise a downwardly and rearwardly extending winglet having one or more wheels for supporting the aircraft.

Drawings

Preferred embodiments of the present invention will now be described by way of specific examples with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram depicting a vertical take-off and landing (VTOL) aircraft of the present invention in a take-off and landing configuration;

FIG. 2 is a schematic diagram depicting the VTOL aircraft of FIG. 1 in a second forward flight configuration;

FIG. 3 is a schematic diagram showing a mounting arrangement for mounting a motor to the aircraft wing of FIGS. 1 and 2 in a vertical (take-off and landing) rotor position;

FIG. 4 is another schematic view of the arrangement of FIG. 3 with the rotor in a partially tilted position;

FIG. 5 is another schematic view of the arrangement of FIG. 3 with the rotor in another tilted position;

FIG. 6 is another schematic view of the arrangement of FIG. 3 with the rotor in a horizontal (forward flight) position;

FIG. 7 is a perspective view depicting another embodiment of a VTOL aircraft;

FIG. 8 is a side view of the wing arrangement of FIG. 7;

FIG. 9 is a top view of the wing arrangement of FIG. 7;

FIG. 10 is a perspective view of the wing arrangement of FIG. 7 with the rotor blades stowed;

FIG. 11A is a schematic side view (vertical rotor axis) showing a mounting arrangement for mounting a motor to an aircraft wing;

FIG. 11B is a perspective view of the mounting arrangement of FIG. 11A;

FIG. 11C is a schematic side view showing the mounting arrangement of FIG. 11A, but with the rotor axis vertical;

FIG. 11D is a perspective view of the mounting arrangement of FIG. 11C;

FIG. 12 is a schematic cross-sectional view depicting a transition between vertical and horizontal for the wing arrangement of the aircraft of any of FIGS. 7-11D;

FIG. 13 is a schematic perspective view of the aircraft in a parked configuration with the access door open;

FIG. 14 is a side view of the aircraft with the rotor depicted in a vertical axis position;

FIG. 15 is a top view of the aircraft with the rotor depicted in a horizontal axis position;

FIG. 16 is a perspective view of the aircraft with the rotor depicted in a vertical axis position; and

figure 17 is a front view of the aircraft with the rotor depicted in a horizontal axis position.

Detailed Description

A Vertical Take Off and Landing (VTOL) aircraft 10 is disclosed. As depicted in the drawings, there are two pairs of wings in the preferred embodiment. Namely, the front wings 20, 22 and the rear wings 30, 32. Each front wing 20, 22 is attached to a laterally opposite region (laterally opposing region, laterally opposite region) of the fuselage 24. Similarly, each rear wing 30, 32 is attached to laterally opposite regions of the fuselage 24. In the embodiment shown in the drawings, the aircraft 10 is depicted as a single or double seat aircraft 10. However, larger multi-person embodiments are also contemplated. The aircraft 10 may be controlled internally by the pilot, or alternatively, it may be remotely controlled.

In the embodiment shown in the drawings, the distal portions of the front and rear wings 20, 22, 30, 32 are connected with a connecting member or web 42 such that the two pairs of wings 20, 22, 30, 32 define a box or closed wing structure.

In another embodiment (not shown), the front and rear airfoils 20, 22, 30, 32 may be strut-supported airfoils connected by tie rods or struts. Strut support wings are generally lighter than conventional cantilevered wings.

Although the VTOL aircraft 10 described herein is a box wing or strut-supporting aircraft 10, those skilled in the art will appreciate that the aircraft 10 may be a conventional cantilevered wing aircraft in which the front wings 20, 22 and the rear wings 30, 32 are separate and not interconnected. Furthermore, the aircraft 10 may have only one pair of wings.

Referring to the drawings, the front wings 20, 22 are vertically separated from the rear wings 30, 32 such that the front wings 20, 22 are located vertically below the rear wings 30, 32.

As depicted in fig. 2, the tip portions 40 of the rear wings 30, 32 extend downwardly and rearwardly. The wing tip section or winglet 40 helps reduce wing tip vortex. Winglets 40 may include one or more wheels 39 (fig. 13 and 14) for supporting aircraft 10 at rest and during landing. The aircraft 10 also has another wheel or set of wheels 41 positioned below the fuselage 24, typically near the front of the fuselage 24. In this way, the rear wheel 39 and the front wheel 41 are located at the apexes of an isosceles triangle. By locating the rear wheels 39 on the winglets 40, the width of the isosceles triangle is maximised, thereby increasing the stability of the aircraft 10.

Referring to the side view of fig. 14, winglet 40 and connecting member 42 together define a generally T-shaped portion of the wing assembly.

Referring to the embodiment of fig. 13-17, the cabin may be accessed through a door or hatch 82 hinged overhead above the occupant by means of a hinge 85. As shown in the embodiment of fig. 13-17, there are two hinges 85 and the door 82 opens upward.

The arrangement of the hinge 85 for securing the upper positioning of the door 82 and the upwardly opening door 82 provide several functional advantages. First, this configuration allows a user to access the nacelle from the front of the aircraft 10 without having to approach the rotor 70. This arrangement makes the exit from the aircraft 10 particularly simple, as the user only has to stand up from a sitting position and move forward, away from the aircraft 10.

The upwardly opening door 82 also provides improved protection against rain during ingress and egress, as the door is normally held above the nacelle when open.

In addition, the door 82 allows the front of the nacelle to be positioned close to the underlying ground surface. The step height (step height) of entering the cabin from the underlying ground surface is about 250mm, which is a great improvement in both entrance/exit comfort and ease compared to other lightweight aircraft.

Referring again to FIG. 2, the proximal side of each winglet 40 is connected to a connecting member 42 that joins adjacent front and rear wings 20, 30. Another connecting member 42 joins adjacent front wing 22 and rear wing 32 on opposite sides of fuselage 24.

Each of the front wings 20, 22 and the rear wings 30, 32 has a fixed leading edge 25, 35. The leading edges 25, 35 have a curved profile in the shape of a portion of an airfoil. Importantly, the leading edge does not rotate or otherwise move relative to the fuselage 24.

On the trailing side of each fixed leading edge 25, 35, the front wing 20, 22 and/or the rear wing 30, 32 has a pivotally mounted aileron or control surface 50. Each control surface 50 pivots between a generally vertical configuration for lifting (as shown in fig. 1) and a generally horizontal configuration for flying forward (as shown in fig. 2).

The control surface 50 may be a single surface that extends continuously along the entire length of the wing 20, 22, 30, 32. Alternatively, each wing 20, 22, 30, 32 may have one or more independently pivotable control surfaces 50 such that the control surfaces 50 can pivot about the leading edges 25, 35 independently of the other control surfaces 50.

The vertical take-off and landing (VTOL) aircraft 10 includes a plurality of electric motors 60. Each motor 60 has a propeller or rotor 70. As depicted, the body portion 62 of each motor 60 is mounted adjacent to the upper or lower surface of the movable control surface 50, typically in front of the fixed leading edges 25, 35. The control surface 50 is rotatable through a range of between about 80 to 100 degrees and preferably through approximately 90 degrees for both horizontal (fig. 2) and vertical (fig. 1) modes of flight.

The motor 60 may be mounted in front of the fixed leading edges 25, 35 enough to enable the rotor blades to fold back and remain clear of the wing structure. However, the preferred embodiment uses a non-folding rotor 70 with a variable pitch mechanism. Fixed pitch blades may also be used.

The motor 60 and control surface 50 have two possible mounting arrangements:

a) Each motor 60 may be pivotally connected to one of the fixed leading edges 25, 35, and the control surface 50 is fixedly secured to the body portion 62 of the motor 60; or alternatively

b) The control surface 50 may be pivotally connected to one of the fixed leading edges 25, 35 and the control surface is fixedly secured to the body portion 62 of the motor 60.

Each motor 60 pivots with the control surface 50 about the leading edge 25, 35 between a first position in which the rotor of each motor 60 has a substantially vertical axis of rotation and a second position in which each rotor of each motor 60 has a substantially horizontal axis of rotation.

In the embodiment depicted in fig. 1-6, at least one of the airfoils 20, 22, 30, 32 has a first motor and a second motor 60 that are offset relative to each other with respect to a plane passing through the control surface 50. In the embodiment shown in fig. 1 to 6, this is achieved by positioning the motors 60 on opposite upper and lower sides of the wings 20, 22, 30, 32. In the embodiment depicted in fig. 1-6, each wing has four motors 60. That is, two motors 60 are mounted above the airfoils 20, 22, 30, 32 and two motors 60 are mounted below the airfoils 20, 22, 30, 32 in an alternating configuration. In another embodiment, each wing 20, 22, 30, 32 has two motors 60.

The motor 60 and its mounting cradle are each mounted to the pivoting control surface 50. Each motor 60 rotates about a hinge point 33. Four motors 60 are mounted with different thrust lines. Specifically, two motors 60 have thrust lines that tend to rotate the control surface 50 horizontally, and the other two motors have thrust lines that tend to rotate the airfoils 20, 22, 30, 32 vertically. When all four motors 60 are operating in unison, the torque counteracts and stability is achieved in the vertical flight mode.

As depicted in fig. 3-6, the sequence of wing adjustments shows the change in the inclination of the motor 60 and control surface 50 when transitioning between the take-off wing pose and the front aircraft wing pose. As shown in those figures, the leading edges 25, 35 are fixed and non-pivoting. Instead, the motor 60 and the control surface 50 pivot in unison.

Referring to fig. 6, when the wing reaches a final horizontal attitude for forward flight, the engagement between the leading edges 25, 35 and the control surface 50 prevents further pivoting of the wings 20, 22, 30, 32. This occurs because the wings 20, 22, 30, 32 and the control surface 50 have complementary engagement surfaces.

A second embodiment of the invention is shown in fig. 7 to 12. In this embodiment, four motors 60 are mounted beneath the wings 20, 22, 30, 32. Specifically, each motor 60 is hingedly affixed to a location below the wing 20, 22, 30, 32, which can be used to form a leading edge slot 72, further improving the lift coefficient and reducing buffet at large angles of inclination in descent.

The leading edge slot 72 is the gap between the leading edges 25, 35 and the sloped control surface 50. The slot 72 is visible in fig. 3, 4, 5 and in the closed position in fig. 6. The leading edge slots 72 can also be seen in fig. 11A.

Referring to fig. 8, in this arrangement, the axes of rotation of the motors 60 are not parallel. Specifically, for each pair of motors 60, each odd motor 60 has a rotation axis XX inclined downward with respect to the control surface 50, and each even motor 60 has a rotation axis YY inclined upward with respect to the control surface 50. In this manner, one of the motors 60 has a thrust line tending to rotate the control surface 50 clockwise and the other motor has a thrust line tending to rotate the control surface 50 counterclockwise. When the pair of motors 60 are operated consistently at similar rotational speeds, the torque counteracts and stability is achieved in the vertical flight mode.

The aircraft 10 provides an individually regulated power supply to each of the electric motors 60. This allows different voltages to be delivered to each motor and, as such, variable power output may be selectively produced by each motor 60 to achieve desired flight conditions, such as left and right turns.

Furthermore, the independent power of the motor 60 enables the motor 60 to be used to tilt the control surface 50 positioned on the trailing edge of the wing 20, 22, 30, 32.

Fig. 11A-11D show side views of the motor 60 mounted to the underside of one of the wings 20, 22, 30, 32. The hinge plates 28 are connected to the stationary front edges 25, 35 and extend downward. The motor 60 is pivotally connected to the hinge plates 28 at hinge point 33. The propeller 70 and the pylon structure are fixed to a control surface 50 which rotates about a hinge point 33.

In a second embodiment, having the motor 60 mounted on the underside of the wing, the sequence of wing adjustments depicted in fig. 11A-11D shows the change in the inclination of the motor 60 and control surface 50 when transitioning between a vertical take-off wing position and a horizontal front aircraft wing position. In the same way as in the first embodiment, the leading edges 25, 35 are fixed and not pivoted, and the motor 60 and the control surface 50 pivot in unison.

Fig. 12 is a schematic cross-sectional view depicting the transition between vertical and horizontal for the wing arrangement of any of fig. 7-11D. As shown in this figure, the vertical and horizontal spacing between the front and rear wings is shown. Fig. 12 also depicts that the thrust lines of adjacent motors on each wing are not parallel, which results in a moment about the hinge point 33 that can be selectively used to rotate to the control surface 50.

In the embodiment depicted in fig. 1-17, two or four motors 60 are mounted to each wing 20, 22, 30, 32. However, additional motors 60 are mounted to the aircraft 10, for example on the wings 20, 22, 30, 32, on the nose of the fuselage 24 or on the wing attachment members 42.

In the embodiment depicted in fig. 15-17, two motors 60 are mounted to each wing 20, 22, 30, 32. By employing a smaller number of motors 60, the diameter of rotor 70 may be increased. As shown in the embodiment of fig. 17, rotor blades 70 have a diameter that overlaps adjacent rotor blades when viewed from the front. To accommodate this overlap, motor 60 is mounted such that each set of rotor blades is offset longitudinally relative to the adjacent set of rotor blades (relative to the axis of rotation) to prevent contact between adjacent rotors, although larger diameter rotors are permitted to be deployed. As shown in fig. 15.

In one embodiment, the hinge mechanism may be integrated into the motor nacelle structure, thereby further reducing the weight of the structure. Another possible improvement is that when there are multiple motor pods, each pod houses a hinge bearing.

Referring to fig. 10, when not in use, the blades of rotor 70 of motor 60 may be folded down. Further, some rotor blades 60 may fold down and back when in forward flight mode, as less propulsion power is typically required in forward flight mode than in take-off and landing.

Advantageously, the aircraft 10 allows for smaller distributed hinge bearings for each motor 60, which may be redundant and of smaller diameter (and thus lighter).

The present invention may provide a notched leading edge that greatly reduces buffeting experienced by a tilting wing aircraft during descent.

Additional motors (not shown) may be mounted to structures other than the wing, such as the fuselage, to generate additional lift and/or forward speed.

Advantageously, the box-like wing structure is aerodynamically more efficient and structurally more efficient (and thus lighter) than a conventional wing of the same size.

Advantageously, the box wing structure provides additional stiffness.

Advantageously, the aircraft 10 reduces the weight of the bearings and tilt structure required as compared to conventional tilt-wing aircraft. This is because conventional tilting wings require a single large bearing pair (one on each side of the aircraft fuselage) with a rotating rigid structure.

Although the invention has been described with reference to specific examples, those skilled in the art will appreciate that the invention may be embodied in many other forms.

Claims

1. A vertical take-off and landing (VTOL) aircraft comprising:

a body;

first and second front wings mounted to opposite sides of the fuselage;

first and second rear wings mounted to opposite sides of the fuselage;

a plurality of motors having rotors and mounted to the wing, the rotors pivoting with the tail control surface between a first position in which each rotor has a substantially vertical axis of rotation and a second position in which each rotor has a substantially horizontal axis of rotation;

wherein at least one of the wings has a first motor with a first rotor and a second motor with a second rotor, each rotor being mounted with non-parallel axes of rotation such that the thrust line of the first rotor and the thrust line of the second rotor are different.

2. The vertical take-off and landing (VTOL) aircraft of claim 1, wherein the thrust line of the first rotor passes angularly above a hinge line and the thrust line of the second rotor passes angularly below the hinge line.

3. The vertical take-off and landing (VTOL) aircraft of claim 1 or 2, wherein the axis of rotation of the first rotor is angled upwardly relative to a plane passing through the nose and tail of the control surface and the axis of rotation of the second rotor is angled downwardly relative to a plane passing through the nose and tail of the control surface.

4. The vertical take-off and landing (VTOL) aircraft of claim 1 or 2, wherein the rotational moments generated by each of the first rotor and the second rotor and acting on the control surface cancel each other out when the first rotor and the second rotor are operating at the same rotational speed.

5. The vertical take-off and landing (VTOL) aircraft of claim 1 or 2, wherein the first and second motors are pivotally mounted to an underside of the fixed leading edge.

6. The vertical take-off and landing (VTOL) aircraft of claim 5, wherein the first and second electric motors are grounded to the tail control surface.

7. The vertical take-off and landing (VTOL) aircraft of claim 1, wherein the first rotor is positioned below a lower surface of the wing and the second rotor is positioned above an upper surface of the wing.

8. The vertical take-off and landing (VTOL) aircraft of claim 1 or 7, wherein the motors and rotors are distributed along the wing at locations below a lower surface of the wing and alternately above an upper surface of the wing.

9. The vertical take-off and landing (VTOL) aircraft of claim 1 or 7, wherein each front wing is connected to an adjacent rear wing by one or more struts or ties.

10. The vertical take-off and landing (VTOL) aircraft of claim 1 or 7, wherein the control surface pivots through a range of about 80 degrees and 100 degrees.

11. The vertical take-off and landing (VTOL) aircraft of claim 10, wherein the control surface pivots through a range of about 90 degrees.

12. The vertical take-off and landing (VTOL) aircraft of claim 1, wherein at least one of the wings has a first motor with a first rotor and a second motor with a second rotor offset relative to an upper surface and a lower surface of the wing.

13. The vertical take-off and landing (VTOL) aircraft of claim 12, wherein the motors and rotors are distributed along the wing at locations below a lower surface of the wing and alternately above an upper surface of the wing.